An end mill used for cutting has a cutting blade on an outer peripheral surface and an end surface and thus, it is capable not only of drilling but also of machining such as face milling, side milling, step milling, grooving, curved surface milling with one mill. Since an expensive metal material is used in the end mill, it is not economical to discard of the blade due to abrasion each time it is worn out. Thus, reusing by recovering a cutting performance has been carried out by polishing the cutting part.
On the other hand, if the polishing of the cutting part is repeated, a polishing margin is exhausted and thus, polishing has a limit. On the other hand, Patent Literature 1 proposes use of a single rotary cutting tool for a long time by forming a third cutting part by machining a first gripping part after a first cutting part and a second cutting part formed at the beginning on both sides of the first gripping part (corresponding to the shank part) are exhausted.